U.S. patent number 8,121,027 [Application Number 12/097,183] was granted by the patent office on 2012-02-21 for access gateway, terminal and method of controlling flow in wireless system.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Norihisa Matsumoto, Yosuke Takahashi, Koji Watanabe.
United States Patent |
8,121,027 |
Watanabe , et al. |
February 21, 2012 |
Access gateway, terminal and method of controlling flow in wireless
system
Abstract
A wireless system includes plural different access networks and
terminals (19, 20) having interfaces corresponding to the plural
different access networks (3, 5, 9, 13). Each of the access
networks includes an access gateway (AGW) performing flow control.
Upon receiving a packet transmission stop signal, the AGW
determines whether a predetermined message transmitting chance is
given. The AGW includes a control unit that transmits a message
that requests a handover to another access network to a terminal
when the message transmitting chance is given. The terminal
includes a unit that performs a handover to another access network,
upon receiving the message.
Inventors: |
Watanabe; Koji (Kokubunji,
JP), Takahashi; Yosuke (Yokohama, JP),
Matsumoto; Norihisa (Fuchu, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
38217748 |
Appl.
No.: |
12/097,183 |
Filed: |
December 27, 2005 |
PCT
Filed: |
December 27, 2005 |
PCT No.: |
PCT/JP2005/023872 |
371(c)(1),(2),(4) Date: |
June 12, 2008 |
PCT
Pub. No.: |
WO2007/074511 |
PCT
Pub. Date: |
July 05, 2007 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20090129275 A1 |
May 21, 2009 |
|
Current U.S.
Class: |
370/229; 370/338;
370/401 |
Current CPC
Class: |
H04L
47/824 (20130101); H04W 36/02 (20130101); H04L
47/70 (20130101); H04L 12/46 (20130101); H04L
12/5692 (20130101); H04W 36/38 (20130101); H04W
36/14 (20130101) |
Current International
Class: |
H04W
4/00 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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8-46643 |
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Feb 1996 |
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JP |
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2003-333639 |
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Nov 2003 |
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JP |
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2005-244524 |
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Sep 2005 |
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JP |
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2005-244525 |
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Nov 2005 |
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JP |
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2005-311702 |
|
Nov 2005 |
|
JP |
|
2005-341610 |
|
Dec 2005 |
|
JP |
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WO 2005/115026 |
|
Dec 2005 |
|
WO |
|
Other References
3GPP2 X.P0011-D, Chapter 3, (Jun. 2005). cited by other .
3GPP2 X.P001-D, Chapter 4, (Jun. 2005). cited by other .
3GPP2X.P0028-200v0.1, x31-20050926-005 (Sep. 2005). cited by other
.
European Search Report in European Patent Application No.
05822541.8 dated Aug. 13, 2010. cited by other.
|
Primary Examiner: Harper; Kevin C
Attorney, Agent or Firm: Brundidge & Stanger, P.C.
Claims
What is claimed is:
1. An access gateway configured to belong to a first access network
in a wireless system, wherein said wireless system includes the
first access network, a second access network, and a terminal
having interfaces corresponding to each of the first and second
access networks, wherein flow in the first access network is
controlled by the access gateway and flow in the second access
network is controlled by a second access gateway, said access
gateway comprising: a unit for receiving a packet transmission stop
signal output by the first access network; and a control unit,
wherein, in response to the unit receiving the packet transmission
stop signal output by the first access network, the control unit
determines whether a predetermined message transmitting chance is
to be given, and in response to determining that the message
transmitting chance is to be given, the control unit transmits a
message to the terminal that requests a handover to the second
access network whose type is different from that of the first
access network.
2. The access gateway according to claim 1, further comprising: a
unit for receiving a message including address information of an
interface of the terminal; and a storage unit for storing the
address information, wherein the control unit manages the address
information, selects a destination from the address information,
and transmits the message.
3. The access gateway according to claim 1, further comprising: a
storage unit for storing transmission information for the terminal,
wherein, when an amount of the transmission information stored in
the storage unit is larger than a threshold value, it is determined
that the message transmitting chance is to be given.
4. The access gateway according to claim 1, further comprising: a
storage unit for storing a communication quality to be provided to
the terminal, wherein the control unit measures the communication
quality to be provided to the terminal and compares the measured
communication quality with the communication quality stored in the
storage unit, and when the measured communication quality is lower
than that stored in the storage unit, it is determined that the
message transmitting chance is to be given.
5. The access gateway according to claim 4, wherein the control
unit measures and compares at least one of a packet loss rate and
latency as the communication quality.
6. The access gateway according to claim 1, wherein the
predetermined message transmitting chance is randomly
determined.
7. The access gateway according to claim 1, further comprising: a
storage unit for storing a communication quality provided to the
terminal, wherein, when the communication quality is within a
predetermined range, it is determined that the predetermined
message transmitting chance is to be given.
8. The access gateway according to claim 7, wherein the
communication quality is at least one of a traffic class, priority,
latency, and a packet loss rate.
9. A flow control method in a wireless system including a first
access network, a second access network, and a terminal having
interfaces corresponding to each of the first and second access
networks, wherein flow in the first access network is controlled by
a first access gateway and flow in the second access network is
controlled by a second access gateway, the method comprising:
allowing the terminal to communicate through the first access
network including the first access gateway, allowing the first
access gateway to determine whether a predetermined message
transmitting chance is to be given in response to the first access
gateway receiving a packet transmission stop signal received from
the first access network; and transmitting a message to the
terminal requesting a handover to the second access network
including the second access gateway, in response to the first
access gateway determining that the message transmitting chance is
to be given.
10. The flow control method in the wireless system according to
claim 9, wherein the handover request message is transmitted to the
terminal through the first access network including the first
access gateway and a first interface of the terminal corresponding
to the first access network including the first access gateway.
11. The flow control method in the wireless system according to
claim 10, wherein, in the first access gateway and the first access
network including the first access gateway, the handover request
message is sent with a priority higher than user data.
12. The flow control method in the wireless system according to
claim 9, wherein the handover request message is transmitted to the
terminal through the second access network not including the first
access gateway, and a second interface of the terminal
corresponding to the second access network.
13. The flow control method in the wireless system according to
claim 9, wherein, in the determination of the predetermined message
transmitting chance, when an amount of the information transmitted
to the terminal is larger than a threshold value, it is determined
that the message transmitting chance is to be given.
14. The flow control method in the wireless system according to
claim 9, further comprising: measuring a communication quality
provided to the terminal; comparing the measured communication
quality with a communication quality to be provided to the terminal
that has been stored in a storage unit beforehand; and determining
that the message transmitting chance is to be given, when the
measured communication quality is lower than that stored in the
storage unit, in the determination of the predetermined message
transmitting chance.
15. The flow control method in the wireless system according to
claim 9, further comprising steps of: managing information of the
communication quality granted by the first access network;
examining whether to perform a handover on a parameter of the
communication quality; and comparing the communication qualities
when it is determined that the handover is performed on the
parameter.
Description
CLAIM OF PRIORITY
The present application claims priority from PCT patent application
PCT/JP2005/023872 filed on Dec. 27, 2005, the content of which is
hereby incorporated by reference into this application.
FIELD OF THE INVENTION
The present invention relates to an access system performing flow
control, a wireless system performing a handover between access
systems, and a flow control method.
BACKGROUND OF THE INVENTION
A method of controlling flow between a PDSN (Packet Data Service
Node), which is an access gateway, and a 1xEv-DO (1x Evolution Data
Only) RAN (Radio Access Network) has been proposed in Chapter 8 of
the NON-PATENT DOCUMENT 1 as a type of wireless system that has
been standardized by 3GPP2 (3.sup.rd Generation Partnership Project
2).
Further, a method of setting QoS (Quality of Service) in a wireless
system has been proposed in the NON-PATENT DOCUMENT 2, which has
been standardized by 3GPP2 (3.sup.rd Generation Partnership Project
2). In the document, Annex.E discloses the format of a QoS
parameter used for signaling, and Annex.F discloses a call flow in
which a mobile station (MS) requests QoS from a network and a RAN
permits the request.
Furthermore, a standard for inter-working between a wireless LAN
and a 1xEv-DO system has been proposed in the NON-PATENT DOCUMENT
3, which has been standardized by 3GPP2 (3.sup.rd Generation
Partnership Project 2).
[NON-PATENT DOCUMENT 1]: X.P0011-D, Chapter 3 (July, 2005)
[NON-PATENT DOCUMENT 2]: X.P0011-D, Chapter 4 (July, 2005)
[NON-PATENT DOCUMENT 3]: X.P0028-200 v0.1, X31-20050926-005
(September, 2005)
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
FIG. 1 shows an example of a wireless system, which is the premise
of the present invention. A Core Network 1 is an IP (Internet
protocol) core network. A Wire-Line Access Network 3 is a wire
access network, a 1xEv-DO RAN 5 is a 1xEv-DO radio access network,
a WLAN RAN 9 is a Wireless LAN (WLAN) radio access network, and a
WiMAX RAN 13 is a WiMAX (Worldwide Interoperability for Microwave
Access) radio access network.
An Access Gate Way (AGW) 8 is a gateway provided at the boundary
between the access network and the core network. An AGW 2 is an
Access Gateway provided between the wire-line access network 3 and
the core network 1. An AGW 4 is an Access Gate Way provided between
the 1xEv-DO RAN 5 and the core network 1, which is called a PDSN.
The AGW 8 is an access gateway provided between the WLAN RAN 9 and
the core network 1, which is called a PDIF (Packet Data
Inter-working Function). An AGW 12 is an Access Gate Way provided
between the WiMAX RAN 13 and the core network 1. An AP 7 is an
access point (AP) of the 1xEv-DO system. An AP 11 is an access
point of the wireless LAN. An AP 15 is an Access Point of the WiMAX
system. An H/R 18 is a HUB or a router including an HAT 19 in the
wire-line access network 3. A PCF (Packet Control Function) 6 is a
packet control function device that transmits packets between the
AP 7 and the AGW 4. An H/R 10 is a hub or a router including the AP
11 in the WLAN RAN 9. An H/R 14 is a hub or a router including the
AP 15 in the WiMAX RAN 13.
HATs 19 and 20 are Hybrid Access Terminals, and include interfaces
for connection to plural different access systems. A CN 16 is a
Correspondence Node that communicates with the HATs 19 and 20. An
HA 17 is a Home Agent of a Mobile IP.
In the prior art, flow control is performed in the access network
in order to prevent packet discard. FIG. 40 shows an example of the
flow control disclosed in NON-PATENT DOCUMENT etc. The flow control
is performed between a network 22 and an AGW 21. The network 22 is
any one of the wire-line access network 3, the 1xEv-DO RAN 5, the
WLAN RAN 9, and the WiMAX RAN 13, and the AGW 21 is any one of the
AGWs 2, 4, 8, and 12. For example, when packet transmission to the
HAT 19 is interrupted due to traffic congestion and the amount of
packet information stored in an apparatus of the network 22 is
larger than a predetermined value, the network 22 transmits a
packet transmission stop signal 23 to the AGW 21. The AGW 21 stops
to transmit packets to the network 22, and stores or discards an IP
packet 25 input from the core network 1.
When the transmission rate of the packet to the HAT 19 is restored
and the amount of packet information staying in the apparatus of
the network 22 is smaller than a predetermined value, the network
22 transmits a packet transmission start signal 24 to the AGW 21.
The AGW 21 resumes the transmission of packets to the network 22
(in this specification, the packet transmission stop signal is
represented by Xoff and the packet transmission start signal is
represented by Xon).
In the prior art, the AGW 21 discards the packet. In the case of
the AGW 21 that stores the IP packet 25, when the AGW 21 receives
Xoff but does not receive Xon because the transmission rate is not
restored, the buffer overflows, which results in the discard of the
packet.
However, it is impractical to perform flow control on all the paths
from the HAT to the CN through a backbone network or the Internet
with whom the operation and management are not integrated.
An object of the present invention is to reduce the amount of
packets discarded by the AGW by significantly reducing the amount
of impact to the core network.
It is possible to consider a flow control signal received by each
AGW as an index for a load applied to the access network.
Another object of the present invention is to provide a method of
performing a handover between new access systems according to a
load applied to the access networks.
Means for Solving the Problem
Some aspects of the present invention will be described briefly as
follows.
According to an aspect of the present invention, an access gateway
for controlling the flow of an access network comprises a receiving
unit for receiving a packet transmission stop signal from the
access network, and a control unit; wherein, upon receiving a
packet transmission stop signal, the control unit determines
whether a predetermined message transmitting chance is given, and
when it is determined that the message transmitting chance is
given, transmits a message that requests a handover to a second
access network whose type is different from that of a first access
network including the access gateway to a terminal belonging to the
access network.
According to another aspect of the present invention, a wireless
system includes plural different access networks and a terminal
having interfaces corresponding to the plural different access
networks. Each of the access networks includes an AGW that performs
flow control. When receiving a packet transmission stop signal, the
AGW determines whether a predetermine message transmitting chance
is given. The AGW includes a control unit that transmits a message
for requiring a handover to another access network to the terminal
when the message transmitting chance is given. In addition, the
terminal includes a unit that performs a handover to another access
network when receiving the message.
Further, preferably, the AGW according to the present invention
includes a unit that transmits the handover request message to the
terminal through an access network including the AGW and an
interface of the terminal corresponding to the access network
including the AGW. In this case, the AGW and the access network
including the AGW transmit the message having higher priority than
user data.
Furthermore, preferably, the AGW according to the present invention
includes a unit that transmits the handover request message to the
terminal through an access network not including the AGW and an
interface of the terminal corresponding to the access network. The
AGW include a storage unit that stores address information and a
control unit that manages the address information, selects a
destination from the address information, and transmits the
message.
According to another aspect of the present invention, a terminal
includes a unit that transmits a message including address
information of an interface of the terminal, which corresponds to
another access network different from one access network, to an AGW
belonging to the one access network connected to the terminal.
Preferably, the AGW according to the present invention includes a
storage unit that stores transmission information for the terminal.
When the amount of transmission information stored in the storage
unit is larger than a threshold value, the AGW determines a chance
to transmit the handover request message.
Further, preferably, the AGW according to the present invention
includes a storage unit that stores a communication quality (QoS)
to be provided to the terminal, and a control unit that measures
the communication quality and compares the measured communication
quality with the communication quality stored in the storage unit.
When the measured communication quality is lower than that stored
in the storage unit, the AGW determines that a message transmitting
chance is given. Preferably, the control unit measures and compares
at least one of a packet loss rate and latency as the communication
quality.
Preferably, the AGW according to the present invention randomly
determines the predetermined message transmitting chance.
Preferably, the AGW includes a storage unit that stores a
communication quality provided to the terminal. When the
communication quality is within a predetermined range, the AGW
determines that the predetermined message transmitting chance is
given. Preferably, the communication quality is any one of a
traffic class, priority, latency, and a packet loss rate.
Effect of the Invention
According to the wireless system according to the present
invention, the access network includes the AGW that performs flow
control. When receiving the packet transmission stop signal, the
AGW determines whether a predetermined message transmitting chance
is given. In addition, the terminal includes a unit that performs a
handover to another access network when receiving the message.
Therefore, when each access system can absorb a traffic load, it is
possible to prevent unnecessary switching to use the access system.
As a result, it is possible to stably use one access system and
thus reduce signaling overhead that accompanies the switching
operation, the number of communication interruptions, or time.
Further, the AGW according to the present invention includes a unit
that stores transmission information for the terminal, and
determines that the transmitting chance of a handover request
message is given when the amount of transmission information stored
in the storage unit is larger than a threshold value. When each
access system cannot absorb a traffic load, switching from the
access system that is currently being used to another access system
is performed. Therefore, it is possible to reduce the possibility
of the AGW of each of the access systems discarding the
packets.
Furthermore, the AGW according to the present invention includes a
storage unit that stores a communication quality provided to the
terminal and a control unit that measures the communication quality
and compares the measured communication quality with that stored in
the storage unit. When the measured communication quality is lower
than that stored in the storage unit, the AGW determines that the
message transmitting chance is given. When each access system
cannot absorb a traffic load and the communication quality
deteriorates, switching from the access system that is currently
being used to another access system is performed. Therefore, it is
possible to reduce the deterioration in communication quality.
Moreover, the AGW according to the present invention includes a
storage unit that stores a communication quality provided to the
terminal, and determines that the message transmitting chance is
given when the communication quality is within a predetermined
range. The AGW can perform a handover between different types of
access systems only when it is necessary to maintain the
communication quality provided to the terminal.
Further, the AGW according to the present invention randomly
determines the predetermined message transmitting chance. When the
AGW collectively performs a handover on all the IP flows receiving
the packet transmission stop signal, there is a concern that a load
is concentrated on a handover destination. However, since the AGW
randomly performs a handover, it is possible to distribute a
load.
The AGW according to the present invention transmits the handover
request message to the terminal through an access network including
the AGW and an interface of the terminal corresponding to the
access network including the AGW. In this case, the AGW and the
access network including the AGW transmit the message having higher
priority than user data. Therefore, if communication is not
completely interrupted, the AGW can transmit the handover request
message to the terminal even though the transmission of the user
data is stopped.
The AGW according to the present invention includes a unit that
transmits the handover request message to the terminal through an
access network not including the AGW and an interface of the
terminal corresponding to the access network. Even though the
communication of the access system used is completely interrupted,
the message can be transmitted through another access system.
Therefore, the AGW can transmit the handover request message to the
terminal.
The terminal according to the present invention includes a unit
that transmits a message including address information of an
interface of the terminal, which corresponds to another access
network different from one access network, to an AGW belonging to
the one access network connected to the terminal. Therefore, the
AGW can obtain the address of a message destination.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, various terminals, an access network, and an access
gateway according to embodiments of the present invention, which
are applicable to the wireless system shown in FIG. 1, will be
described with reference to the accompanying drawings.
[Example of HAT]
First, an example of the structure of an HAT according to a first
embodiment of the present invention is shown in FIG. 2. As
described above, an HAT 19 (and HAT 20) is a hybrid access terminal
that includes an interface for connection to plural different
access systems. In FIG. 2, a 1xEv-DO interface (1xEv-DO IF) 34 is
an interface for connection to a 1xEv-DO RAN 5. A BB (Baseband
Unit) 38 processes the baseband signals transmitted or received to
or from the 1xEv-DO system. For example, the BB 38 modulates a
transmission signal, supplements the synchronization of received
signals, and demodulates the received signals. An IF (interface) 37
processes an intermediate frequency (IF) signal of the 1xEv-DO
system. The IF 37 performs DA (Digital-to-Analog) conversion on the
baseband signal of 1xEv-DO input from the BB 38, and converts the
converted signal into an intermediate frequency signal, and outputs
the signal to an RF (Radio Frequency) unit 36. In addition, the IF
37 performs AD (Analog-to-Digital) conversion on an RF signal of
1xEv-DO input from the RF unit 36, and outputs the converted signal
to the BB 38. The RF unit 36 processes the radio frequency (RF)
signal of 1xEv-DO. The RF unit 36 up-converts the signal input from
the IF 37 into an RF signal, amplifies transmission power, and
outputs the RF signals to an antenna 35. In addition, the RF unit
36 down-converts the RF signal received from the antenna 35 into an
intermediate frequency signal, and outputs the signal to the IF
37.
A WLAN interface (WLAN IF) 39 is an interface for connection to a
WLAN RAN 9. A BB 43 processes the baseband signals transmitted or
received to or from a wireless LAN. For example, the BB 43
modulates a transmission signal, supplements the synchronization of
received signals, and demodulates the received signals. An IF 42
processes an intermediate frequency (IF) signal of the wireless
LAN. The IF 42 performs DA (Digital-to-Analog) conversion on the
baseband signal of the wireless LAN input from the BB 43, and
converts the converted signal into an intermediate frequency
signal, and outputs the signal to an RF unit 41. In addition, the
IF 42 performs AD (Analog-to-Digital) conversion on an RF signal of
the wireless LAN input from the RF unit 41, and outputs the
converted signal to the BB 43. The RF (Radio Frequency) unit 41
processes the radio frequency (RF) signal of the wireless LAN. The
RF unit 41 up-converts the signal input from the IF 42 into an RF
signal, amplifies transmission power, and outputs the RF signal to
an antenna 40. In addition, the RF unit 41 down-converts the RF
signal received from the antenna 40 into an intermediate frequency
signal, and outputs the signal to the IF 42.
A WiMAX interface (WiMAX IF) 44 is an interface for connection to a
WiMAX RAN 13. A BB 48 processes the baseband signals transmitted or
received to or from a WiMAX system. For example, the BB 48
modulates a transmission signal, supplements the synchronization of
received signals, and demodulates the received signals. An IF 47
processes an intermediate frequency (IF) signal of the WiMAX
system. The IF 47 performs DA (Digital-to-Analog) conversion on the
baseband signal of the WiMAX system input from the BB 48, and
converts the converted signal into an intermediate frequency
signal, and outputs the signal to an RF unit 47. In addition, the
IF 47 performs AD (Analog-to-Digital) conversion on an RF signal of
the WiMAX system input from the RF unit 46, and outputs the
converted signal to the BB 48. The RF (Radio Frequency) unit 46
processes the radio frequency (RF) signal of the WiMAX system. The
RF unit 46 up-converts the signal input from the IF 47 into an RF
signal, amplifies transmission power, and outputs the RF signal to
an antenna 45. In addition, the RF unit 46 down-converts the RF
signal received from the antenna 45 into an intermediate frequency
signal, and outputs the signal to the IF 47.
A wire-line interface (wire-line IF) 49 is an interface for
connection to a wire-line network 3.
A control unit 31 manages the overall operation of the access point
(AP). The control unit 31 performs various control processes, such
as a process of composing, decomposing, discarding packets that are
received or to be transmitted, a process of controlling the
transmission timing of packets, a process of managing information
in a storage unit 32, a process of transmitting messages, a process
of analyzing received messages, and handover corresponding to the
received message, and also executes application software for a
conference call. The storage unit 32 stores management information
including data that is received or to be transmitted, QoS
information, and address information of each interface. A UIF 33 is
a user interface, such as a keyboard, a display, or a speaker.
[Example of AP]
FIG. 3 shows an example of the structure of an AP (an AP 7, an AP
11, or an AP 15) according to this embodiment of the invention. In
FIG. 3, a network interface (NW IF) 55 is for connection to a PCF
6, an H/R 10, or an H/R 14. A BB 54 processes received baseband
signals or baseband signals to be transmitted. For example, the BB
54 modulates a transmission signal, supplements the synchronization
of received signals, and demodulates the received signals. An IF 53
processes an Intermediate Frequency (IF) signal. The IF 53 performs
DA (Digital-to-Analog) conversion on the baseband signal input from
the BB 54, and converts the converted signal into an intermediate
frequency signal, and outputs the signal to an RF unit 52. In
addition, the IF 53 performs AD (Analog-to-Digital) conversion on
the signal input from the RF unit 52, and outputs the converted
signal to the BB 54. The RF (radio frequency) unit 52 processes
radio frequency (RF) signals. The RF unit 52 up-converts the signal
input from the IF 53 into an RF signal, amplifies transmission
power, and outputs the RF signal to an antenna 51. In addition, the
RF unit 52 down-converts the RF signal received from the antenna 51
into an intermediate frequency signal, and outputs the signal to
the IF 53. A control unit 57 manages the overall operation of the
AP. In addition, the control unit 57 performs a process of
composing messages and a process of transmitting the messages. That
is, the control unit 57 performs a process of composing,
decomposing, or discarding wireless transmission units and packets
that are transmitted or received through the NW IF 55, a process of
controlling the transmission timing of the wireless transmission
unit using a timer 56, a process of managing information in a
storage unit 58, and a flow control process. The storage unit 58
stores management information, such as received data, data to be
transmitted, and QoS information. The timer 56 is a time
counter.
[Example of H/R]
FIG. 4 shows an example of the structure of an H/R (an H/R 10, an
H/R 14, or an H/R 18) according to this embodiment of the
invention. In FIG. 4, an NW IF 61 is a network interface for
connection to an AGW, and an NW IF 62 is a network interface for
connection to an AP or an HAT. An SW 64 is a switch for exchanging
packets on the basis of the address information in the headers of
the packets. A control unit 65 performs a process of managing
information stored in a storage unit 63, a process of composing,
decomposing, or transmitting/receiving packets, and a flow control
process. The storage unit 37 stores packet data that is received or
to be transmitted and management information required for flow
control.
[Example of PCF]
FIG. 5 shows an example of the structure of a PCF 6 according to
this embodiment of the invention. In FIG. 5, an NW IF 71 is a
network interface for connection to an AP, and an NW IF 76 is a
network interface for connection to an AGW. The SWs 72 and 75 are
switches for exchanging packets. A control unit 73 manages the
overall operation of the PCF 6. A Traffic Controller (TC) 74 is for
composing, decomposing, or transmitting/receiving the packets
transmitted by the PCF 6.
FIG. 6 shows an example of the structure of the TC 74 according to
this embodiment of the invention. A storage unit 77 stores packets
that are received or to be transmitted and management information.
A CPU 78 performs a process of managing information stored in the
storage unit 77, a packet transmitting/receiving process of
composing, decomposing, or discarding packets, and a flow control
process.
[Example of AGW]
FIG. 7 shows an example of the structure of an AGW (an AGW 2, an
AGW 4, an AGW 8, or an AGW 12) according to this embodiment of the
invention. In FIG. 7, an NW IF 86 is a network interface for
connection to an access network. Packets having formats
corresponding to each access network are transmitted or received
through the NW IF 86. An NW IF 87 is a network interface for
connection to a core network 1. IP packets are transmitted or
received through the NW IF 87. A storage unit 82 stores management
information, such as packets that are received or to be
transmitted, address information, QoS information, and information
required for flow control. A control unit 83 performs a process of
managing information stored in the storage unit 82, a packet
transmitting/receiving process of composing, decomposing, or
discarding the packets transmitted to the access network and the IP
packets, a flow control process, a process of measuring QoS, a
process of determining a message transmitting chance, and a process
of transmitting a message for requiring a handover to the HAT. A
UIF 84 is a user interface. A timer 85 is a time counter, and is
used to measure the time for which the packet is stored in the
storage unit 82.
[Example of HA]
An HA 17 is a home agent of a mobile IP. FIG. 8 shows an example of
the structure of the HA 17 according to this embodiment of the
invention. In FIG. 8, an NW IF 90 is a network interface for
connection to the core network 1. A storage unit 88 stores
management information, such as packets that are received or to be
transmitted, address information, QoS information, and information
required for flow control. A control unit 89 performs a process of
composing or decomposing packets, a process of analyzing messages,
and a process of making messages, and a process of managing
information stored in the storage unit.
[Example of CN]
FIG. 9 shows an example of the structure of a CN 16 that
communicates with the HAT according to this embodiment of the
invention. In FIG. 9, an NW IF 96 is a network interface for
connection to the core network 1. A storage unit 92 stores
information or packets that are received or to be transmitted. A
control unit 93 performs a process of composing or decomposing
packets, a process of managing information stored in the storage
unit, and a process of executing various applications. A UIF 94 is
a user interface. In this embodiment, the CN 16 is connected to the
core network by wire, but the HAT may communicate with a wireless
terminal.
[Example of Flow Control Corresponding to Priority]
Next, an example of flow control corresponding to priority
according to this embodiment of the invention will be described
below.
FIG. 10 shows a downstream (toward HAT) transmission buffer
provided in each of the storage units of the AP, the PCF, the H/R,
and the AGW (the storage unit 58, the storage unit 77 of the PCF,
the storage unit 63 of the H/R, or the storage unit 82 of the AGW).
Each of the control units of the AP, the PCF, the H/R, and the AGW
(the control unit 57, the CPU 78 of the PCF, the control unit 65 of
the H/R, or the control unit 83 of the AGW) stores a high-priority
packet in a high-priority buffer 26 and a low-priority packet in a
low-priority buffer 27, with reference to priority designated in
the header of the transmission packet. In addition, each of the
control units of the AP, the PCF, the H/R, and the AGW reads out
the packet from the high-priority buffer 26 earlier than the packet
in the low-priority buffer 27, and transmits the read packet in the
downstream direction.
In FIG. 10, the packet of flow 1 has high priority, and the packet
of flow 2 has low priority. The packet of the flow 1 is stored in
the high-priority buffer 26, and the packet of the flow 2 is stored
in the low-priority buffer 27. In addition, the packet of the flow
1 is transmitted toward the HAT earlier than the packet of the flow
2. The priority designated in the header, which is referred by the
control unit, may be, for example, DSCP (DiffServ Code Point) of
the IP packet.
User data is transmitted through the flow 2, and control data
including a Hand Over Request (HOR) message, which will be
described below, transmitted from the AGW to the HAT is transmitted
through the flow 1. The user data is used for the user of the HAT
to execute applications, such as audio conference or file
download.
When traffic congestion occurs in a wireless transmission line, the
amount of user data transmitted increases since the control data
has higher priority. The amount of user data in the AP is larger
than a predetermined value, the control unit 57 of the AP transmits
a packet stop signal for flow control to the PCF or the H/R. The
PCF or the H/R receives the packet stop signal and stores the
packet of the user data in the downstream direction in the
low-priority buffer 27. In addition, when the traffic congestion is
not restored, the amount of packets of the user data stored in the
storage unit of the PCF or the H/R is larger than a predetermined
value, and the CPU 78 of the PCF or the control unit 65 of the H/R
transmits a packet stop signal 23 to the AGW, as shown in FIG.
40.
Similarly, when traffic congestion occurs in a wire transmission
line of the access network, the packet stop signal 23 for user data
is transmitted to the AGW of each access network. For example, when
traffic congestion occurs between the HAT 19 and the H/R 18, the
H/R 18 starts to store the packets of the user data in the
downstream direction in the low-priority buffer 27. In addition,
when the traffic congestion is not restored, the amount of packets
of the user data stored in the storage unit of the H/R is larger
than a predetermined value, and the control unit 65 of the H/R 18
transmits the packet stop signal 23 to the AGW, as shown in FIG.
40.
The control unit 83 of the AGW receives the packet stop signal 23
and stores the packets of the user data in the downstream direction
in the low-priority buffer 27. When the traffic congestion is not
restored and the amount of packets of the user data stored in the
storage unit 82 is larger than a predetermined value, the control
unit 83 of the AGW transmits an HOR message as a packet of the flow
1. The HOR message is received by the PCF or the H/R and stored in
the high-priority buffer 26. The HOR message is transmitted to the
AP prior to information of the low-priority buffer 27. In addition,
the HOR message is received by the AP and stored in the
high-priority buffer 26. The HOR message is transmitted to the HAT
prior to information of the low-priority buffer 27.
As such, when communication is not completely interrupted, the AGW
can transmit the HOR message to the HAT even when the transmission
of the user data is stopped due to flow control according to
priority.
[Example of HO from 1xEv-DO to WLAN that Transmits HOR in Flow
Control According to Priority]
FIG. 11 shows an example of a call flow when the AGW transmits an
HOR message by the flow control according to priority and the HAT
performs a handover from the 1xEv-DO system to the wireless
LAN.
First, the HAT 19 is connected to the 1xEv-DO RAN 5 and
communicates with the CN 16 by an IP flow (IP flow 101). The IP
flow is a continuous series of IP packets of the same source
address and destination address. In particular, the IP flow 101 is
a series of IP packets including user data.
When traffic congestion occurs in a wireless transmission line of
the 1xEv-DO or the 1xEv-DO RAN 5, the PCF 6 of the 1xEv-DO RAN 5
transmits a packet stop signal (Xoff) 102 for the IP flow 101 to
the AGW 4.
The AGW 4 determines whether to transmit an HOR message for
requesting a handover to the HAT 19. For example, the control unit
83 of the AGW 4 determines that an HOR message transmitting chance
103 is given when the capacity of the low-priority buffer 27 in the
storage unit 82 is larger than a threshold value. When the HOR
message transmitting chance 103 is given, the control unit 83
creates a packet 104 including the HOR message, and transmits it as
control data to the HAT 19 through the NW IF 86.
The message format will be described below. FIG. 19 shows an
example of the format of the packet 104. In addition, FIG. 23 shows
an example of the format of the HOR message included in the packet
104.
The packet 104 is received by the 1xEv-DO IF 34 of the HAT 19
through the 1xEv-DO RAN 5. The control unit 31 of the HAT 19
analyzes the HOR message included in the packet 104, and determines
an access system, which is a handover destination. It is assumed
that the control unit 31 of the HAT 19 determines a wireless LAN as
the access system, which is the handover destination. The control
unit 31 of the HAT 19 transmits or receives a message string 105
required for the handover, and performs a predetermined handover
disclosed in, for example, the NON-PATENT DOCUMENT 3. The HAT 19 is
connected to the WLAN RAN 9, performs switching from the IP flow
101 to an IP flow 106, and communicates with the CN 16.
According to this embodiment, when each access system can absorb a
traffic load, it is possible to prevent unnecessary switching to
use the corresponding access system. Since one access system can be
stably used, it is possible to reduce signaling overhead that
accompanies the switching operation, the number of communication
interruptions, or time.
Further, the access network transmits the message having higher
priority than the user data. Therefore, if communication is not
completely interrupted, the AGW can transmit a message for
requiring a handover to a terminal even when the transmission of
the user data is stopped.
[Example of HO from WLAN to 1xEv-DO that Transmits HOR in Flow
Control According to Priority]
FIG. 12 shows an example of a call flow when the AGW transmits an
HOR message by the flow control according to priority and the HAT
performs a handover from the wireless LAN to the 1xEv-DO system.
First, the HAT is connected to the WLAN RAN 9, and communicates
with the CN 16 by the IP flow 107. The IP flow 107 is an IP packet
string including user data.
When traffic congestion occurs in a wireless transmission line of
the wireless LAN or the WLAN RAN 9, the H/R 10 of the WLAN RAN 9
transmits a packet stop signal 108 for the IP flow 107 to the AGW
8. The AGW 8 determines whether to transmit an HOR message for
requesting a handover to the HAT 19. For example, the control unit
83 of the AGW 8 determines that an HOR message transmitting chance
109 is given when the capacity of the low-priority buffer 27 in the
storage unit 82 is larger than a threshold value. When the HOR
message transmitting chance 109 is given, the control unit 83
creates a packet 110 including the HOR message, and transmits it as
control data to the HAT 19 through the NW IF 86. The packet 110 is
received by the WLAN IF 39 of the HAT 19 through the WLAN RAN 9.
The control unit 31 of the HAT 19 analyzes the HOR message included
in the packet 110, and determines an access system, which is a
handover destination. It is assumed that the control unit 31 of the
HAT 19 determines a 1xEv-DO system as the access system, which is a
handover destination. The control unit 31 of the HAT 19 transmits
or receives a message string 111 required for the handover, and
performs a predetermined handover disclosed in, for example, the
NON-PATENT DOCUMENT 3. The HAT 19 is connected to the 1xEv-DO RAN
5, performs switching from the IP flow 107 to an IP flow 112, and
communicates with the CN 16.
According to this embodiment, when each access system can absorb a
traffic load, it is possible to prevent unnecessary switching to
use the corresponding access system. Since one access system can be
stably used, it is possible to reduce signaling overhead that
accompanies the switching operation, the number of communication
interruptions, or time.
Further, the access network transmits the message having higher
priority than the user data. Therefore, if communication is not
completely interrupted, the AGW can transmit a message for
requiring a handover to a terminal even when the transmission of
the user data is stopped.
[Example of HO from 1xEv-DO to WLAN that Transmits HOR Through
Different Types of Systems]
Even when the communication of a certain access system is
completely interrupted, the AGW can transmit an HOR message to the
HAT through another access system. An example of the handover from
the 1xEv-DO system to the wireless LAN in this case will be
described below.
FIG. 13 shows an example of a call flow when the AGW of the 1xEv-DO
system transmits an HOR message to the HAT 19 through the WLAN RAN
9, with the communication of the 1xEv-DO system being interrupted,
and the HAT 19 performs a handover from the 1xEv-DO RAN 5 to the
WLAN RAN 9.
When the HAT 19 enters a service area of the AP 7 of the 1xEv-DO
RAN 5, the HAT 19 transmits or receives a message string 114 and
performs a predetermined authentication procedure or a
communication line establishment procedure. These procedures allow
the IP address of the 1xEv-DO IF 34 of the HAT 19 to be settled.
That is, in a destination network, a Care-of Address (CoA) of the
mobile IP allocated to the 1xEv-DO IF 34 and the address of the
home agent (HA 17) of the mobile IP used by the 1xEv-DO IF 34 are
settled.
The HAT 19 transmits to the HA 17 a packet 115 including a
Registration ReQuest (RRQ) message of the mobile IP and an AddRess
(ADR) message, which is address information of an interface of an
access system with which the HAT 19 can communicate other than the
1xEv-DO IF 34.
FIG. 15 shows an example of the format of the packet 115.
When receiving the packet 115, the control unit 83 of the AGW 4
analyzes the ADR message and registers information of the ADR
message in an ADR table of the storage unit 82. In addition, the
control unit 83 of the AGW 4 extracts only the registered ADR
message from the packet 115 to create a packet 116, and transmits
the packet 116 to the HA 17.
FIG. 16 shows an example of the format of the packet 116.
The HA 17 registers the IP address information of the 1xEv-DO IF 34
in a table of the storage unit 88, and responds to a Registration
ResPonse (RRP) message 117 of the mobile IP. The RRQ message, the
format of the RRQ message, and the process performed by the HA 17
may be defined by the mobile IP. FIGS. 20 and 21 show examples of
the RRQ message and the format of the RRQ message,
respectively.
The transmission and reception of an IP flow 118 starts between the
HAT 19 and CN 16. The packet of the IP flow 118 transmitted from
the CN to the HAT 19 is received by the NW IF 90 of the HA 17. The
control unit 89 of the HA 17 encapsulates the packet to make an IP
packet, sets a destination with reference to the address table of
the storage unit 88, and transmits the packets through the NW IF
90. In addition, the packet of the IP flow 118 is received by the
1xEv-DO IF 34 of the HAT 19 through the AGW 4 and the 1xEv-DO RAN
5.
When the HAT 19 enters a service area of the AP 11 of the WLAN RAN
9, the HAT 19 transmits or receives a message string 119 and
performs a predetermined authentication procedure or a
communication line establishment procedure. These procedures allow
the IP address of the WLAN IF 39 of the HAT 19 to be settled. That
is, in a destination network, a Care-of Address (CoA) of the mobile
IP allocated to the WLAN IP 39 and the address of the home agent
(HA 17) of the mobile IP used by the WLAN IF 39 are settled. The
HAT 19 transmits to the HA 17 a packet 120 including an RRQ message
of the mobile IP and an ADR message, which is address information
of an interface of an access system with which the HAT 19 can
communicate other than the WLAN IF 39. Now, the HAT 19 transmits a
message to add the address information of the 1xEv-DO IF 34.
FIG. 15 shows an example of the format of the packet 120.
When receiving the packet 120, the control unit 83 of the AGW 8
analyzes the ADR message and registers information of the ADR
message in the ADR table of the storage unit 82. In addition, the
control unit 83 of the AGW 8 extracts only the registered ADR
message from the packet 120 to create a packet 121, and transmits
the packet 121 to the HA 17.
FIG. 16 shows an example of the format of the packet 121.
The HA 17 registers the IP address information of the WLAN IF 39 in
the table of the storage unit 88, and responds to an RRP message
122 of the mobile IP. FIGS. 20 and 21 show examples of the RRQ
message and the format of the RRQ message, respectively.
The control unit 31 of the HAT 19 updates the address information
stored in the AGWs of all the access systems connected thereto,
according to the variation of the connection conditions. Since the
number of interfaces of new access systems connected to the WLAN
PAN 9 for communication increases, the HAT 19 transmits a packet
123 including an ADR message to the AGW 4 in order to add address
information.
FIG. 17 shows an example of the format of the packet 123.
When receiving the packet 123, the control unit 83 of the AGW 4
analyses the message included in the packet and registers
information of the ADR message in the ADR table of the storage unit
82. Now, the control unit 83 registers IP address information of
the WLAN IF 39 in the ADR table of the storage unit 82.
Even after the HAT 19 is connected to the WLAN RAN 9, an IP flow
124 is transmitted or received between the HAT 19 and the CN 16
through the 1xEv-DO RAN 5. It is assumed that traffic congestion
occurs in the wireless transmission line of the 1xEv-DO system or
the 1xEv-DO RAN 5.
A packet stop signal 125 for the IP flow 118 is transmitted from
the PCF 6 of the 1xEv-DO RAN 5 to the AGW 4. The AGW 4 determines
whether an HOR message transmitting chance 126 for handover to the
HAT 19 is given. An algorithm for determining the HOR message
transmitting chance will be described below. For example, the
control unit 83 of the AGW 4 determines that the HOR message
transmitting chance 126 is given when the capacity of the buffer
for transmitting the IP flow 118 provided in the storage unit 82 is
larger than a threshold value. When the HOR message transmitting
chance is given, the control unit 83 creates a packet 127 including
the HOR message, and transmits the packet to the HAT 19 through the
NW IF 87.
FIG. 19 shows an example of the format of the packet 127. FIG. 23
shows an example of the format of the HOR message included in the
packet 127.
The control unit 83 sets the IP address information of the WLAN IF
39 updated with the packet 123 as a destination address of a header
(IP header 214) of the packet 127, with reference to the ADR table
of the storage unit 83. The packet 127 is transmitted to the HA 17
and is encapsulated according to the process of the mobile IP.
Then, the packet is transmitted to the HAT 19. The encapsulated
packet 128 is received by the WLAN IF 39 of the HAT 19 through the
WLAN RAN 9. The control unit 31 of the HAT 19 analyzes the HOR
message of the packet 128, and determines an access system, which
is a handover destination. It is assumed that the control unit 31
of the HAT 19 determines a wireless LAN as the access system, which
is the handover destination. In addition, the control unit 31 of
the HAT 19 transmits or receives a message string 129 required for
handover, and performs a predetermined handover procedure. The HAT
19 switches the IP flow 124 to an IP flow 130 passing through the
WLAN RAN 9, and communicates with the CN 16.
According to this embodiment, when each access system can absorb a
traffic load, it is possible to prevent unnecessary switching for
using the corresponding access system. Even when the communication
of the access system used is completely interrupted, it is possible
to transmit messages through another access system, and thus the
AGW can transmit a handover request message to the terminal. That
is, when each access system cannot absorb a traffic load, switching
from the access system that is currently being used to another
access system is performed. Therefore, it is possible to reduce the
possibility of the AGW of each of the access systems discarding the
packets.
[Example of HO from WLAN to 1xEv-DO that Transmits HOR Through
Different Types of Systems]
An example of handover from the wireless LAN to the 1xEv-DO system
will be described below. FIG. 14 shows an example of a call flow
when the AGW of the wireless LAN transmits an HOR message to the
HAT 19 through the 1xEv-DO RAN 5, with the communication of the
wireless LAN being interrupted, and the HAT 19 performs a handover
from the WLAN RAN 9 to the 1xEv-DO RAN 5.
When the HAT 19 enters a service area of the AP 7 of the 1xEv-DO
RAN 5, the HAT 19 transmits or receives a message string 134 and
performs a predetermined authentication procedure or a
communication line establishment procedure. These procedures allow
the IP address of the 1xEv-DO IF 34 of the HAT 19 to be settled.
That is, in a destination network, a Care-of Address (CoA) of the
mobile IP allocated to the 1xEv-DO IF 34 and the address of the
home agent (HA 17) of the mobile IP used by the 1xEv-DO IF 34 are
settled.
The HAT 19 transmits to the HA 17 a packet 135 including an RRQ
message of the mobile IP and an ADR message, which is address
information of an interface of an access system with which the HAT
19 can communicate other than the 1xEv-DO IF 34.
FIG. 15 shows an example of the format of the packet 135.
When receiving the packet 135, the control unit 83 of the AGW 4
analyzes the ADR message and registers information of the ADR
message in the ADR table of the storage unit 82. In addition, the
control unit 83 of the AGW 4 extracts only the registered ADR
message from the packet 135 to create a packet 136, and transmits
the packet 136 to the HA 17.
FIG. 16 shows an example of the format of the packet 136.
The HA 17 registers the IP address information of the 1xEv-DO IF 34
in the table of the storage unit 88, and responds to a Registration
ResPonse (RRP) message 137 of the mobile IP. The RRQ message, the
format of the RRQ message, and the process performed by the HA 17
may be defined by the mobile IP.
FIGS. 20 and 21 show examples of the RRQ message and the format of
the RRQ message, respectively.
When the HAT 19 enters a service area of the AP 11 of the WLAN RAN
9, the HAT 19 transmits or receives a message string 139 and
performs a predetermined authentication procedure or a
communication line establishment procedure. These procedures allow
the IP address of the WLAN IF 39 of the HAT 19 to be settled. That
is, in a destination network, a Care-of Address (CoA) of the mobile
IP allocated to the WLAN IP 39 and the address of the home agent
(HA 17) of the mobile IP used by the WLAN IF 39 are settled. The
HAT 19 transmits to the HA 17 a packet 140 including an RRQ message
of the mobile IP and an ADR message, which is address information
of an interface of an access system with which the HAT 19 can
communicate other than the WLAN IF 39. The HAT 19 transmits a
message to add the address information of the 1xEv-DO IF 34.
FIG. 15 shows an example of the format of the packet 140.
When receiving the packet 140, the control unit 83 of the AGW 8
analyzes the ADR message and registers information of the ADR
message in the ADR table of the storage unit 82. In addition, the
control unit 83 of the AGW 8 extracts only the registered ADR
message from the packet 140 to create a packet 141, and transmits
the packet 141 to the HA 17.
FIG. 16 shows an example of the format of the packet 141.
The HA 17 registers the IP address information of the WLAN IF 39 in
the table of the storage unit 88, and responds to an RRP message
142 of the mobile IP.
FIGS. 20 and 21 show examples of the RRQ message and the format of
the RRQ message, respectively.
The control unit 31 of the HAT 19 updates the address information
stored in the AGWs of all the access systems connected thereto,
according to the variation of the connection conditions. Since the
number of interfaces of new access systems connected to the WLAN
RAN 9 for communication increases, the HAT 19 transmits a packet
143 including an ADR message to the AGW 4 in order to add address
information.
FIG. 17 shows an example of the format of the packet 143.
When receiving the packet 143, the control unit 83 of the AGW 4
analyses the message included in the packet and registers
information of the ADR message in the ADR table of the storage unit
82. Now, the control unit 83 registers the IP address information
of the WLAN IF 39 in the ADR table of the storage unit 82.
After the HAT 19 is connected to the WLAN RAN 9, the transmission
and reception of an IP flow 144 starts between the HAT 19 and CN
16. The packet of the IP flow 144 transmitted from the CN to the
HAT 19 is received by the NW IF 90 of the HA 17. The control unit
89 of the HA 17 encapsulates the packet to make an IP packet, sets
a destination with reference to the address table of the storage
unit 88, and transmits the packet through the NW IF 90. In
addition, the packet of the IP flow 144 is received by the WLAN IF
39 of the HAT 19 through the AGW 8 and the WLAN RAN 9.
It is assumed that traffic congestion occurs in the wireless
transmission line of the 1xEv-DO system or the WLAN RAN 9. A packet
stop signal 145 for the IP flow 144 is transmitted from the H/R 10
of the WLAN RAN 9 to the AGW 8. The AGW 8 determines whether an HOR
message transmitting chance 146 for handover to the HAT 19 is
given. For example, the control unit 83 of the AGW 8 determines
that the HOR message transmitting chance 146 is given when the
capacity of the buffer for transmitting the IP flow 144 provided in
the storage unit 82 is larger than a threshold value. When the HOR
message transmitting chance is given, the control unit 83 creates a
packet 147 including the HOR message, and transmits the packet to
the HAT 19 through the NW IF 87.
FIG. 19 shows an example of the format of the packet 147. FIG. 23
shows an example of the format of the HOR message included in the
packet 147.
The control unit 83 sets the IP address information of the 1xEv-DO
IF 34 as a destination address of a header (IP Header 214) of the
packet 147, with reference to the ADR table of the storage unit 83.
The packet 147 is transmitted to the HA 17 and is encapsulated
according to the process of the mobile IP. Then, the packet is
transmitted to the HAT 19. The encapsulated packet 148 is received
by the 1xEv-DO IF 34 of the HAT 19 through the 1xEv-DO RAN 5. The
control unit 31 of the HAT 19 analyzes the HOR message of the
packet 148, and determines an access system, which is a handover
destination. It is assumed that the control unit 31 of the HAT 19
determines a 1xEv-DO system as the access system, which is the
handover destination. In addition, the control unit 31 of the HAT
19 transmits or receives a message string 149 required for
handover, and performs a predetermined handover procedure. The HAT
19 switches the IP flow 144 to an IP flow 150 passing through the
1xEv-DO RAN 5, and communicates with the CN 16.
According to this embodiment, when each access system can absorb a
traffic load, it is possible to prevent unnecessary switching for
using the corresponding access system. Even when the communication
of the access system used is completely interrupted, it is possible
to transmit messages through another access system, and thus the
AGW can transmit a handover request message to the terminal. That
is, when each access system cannot absorb a traffic load, switching
from the access system that is currently being used to another
access system is performed. Therefore, it is possible to reduce the
possibility of the AGW of each of the access systems discarding the
packets.
[Example of Format of RRQ+ADR Packets]
FIG. 15 shows an example of the format of the packets 115 and 135
including the RRQ message and the ADR message. An IP header 201 is
a header of an IP packet. A UDP header 202 is a header of a User
Datagram Protocol (UDP) packet. An RRQ 203 indicates an RRQ
message. An ADR 204 indicates an ADR message.
[Example of Format of RRQ Packet]
FIG. 16 shows an example of the format of the packet including the
RRQ message. An IP header 205 is a header of an IP packet. A UDP
header 206 is a header of a User Datagram Protocol (UDP) packet. An
RRQ 207 indicates an RRQ message.
[Example of Format of ADR Packet]
FIG. 17 shows an example of the format of the packet including the
ADR message. An IP header 208 is a header of an IP packet. A UDP
header 209 is a header of a User Datagram Protocol (UDP) packet. An
ADR 210 indicates an ADR message.
[Example of Format of RRP Packet]
FIG. 18 shows an example of the format of the packet including the
RRP message. An IP header 211 is a header of an IP packet. A UDP
header 212 is a header of a User Datagram Protocol (UDP) packet. An
RRP 213 indicates an RRP message.
[Example of Format of HOR Packet]
FIG. 19 shows an example of the format of the packet including the
HOR message. An IP header 214 is a header of an IP packet. A UDP
header 215 is a header of a User Datagram Protocol (UDP) packet. A
HOR 216 indicates an HOR message.
[Example of Format of RRQ Message]
FIG. 20 shows an example of the format of the RRQ message. A
Control field 221 indicates control information and includes an
identifier indicating the RRQ message. An HoA (Home address) field
222 indicates the home address of the interface of the HAT. In this
embodiment, the interface of the HAT is any one of the 1xEv-DO IF
34, the WLAN IF 39, the WiMAX IF 44, and the wire-line IF 49. An HA
223 indicates the address of a home agent. A CoA 224 indicates the
care-of address of the interface of the HAT. An ID 225 is
information for checking whether the message is correct.
[Example of Format of RRP Message]
FIG. 21 shows an example of the format of the RRP message. A
Control field 231 indicates control information and includes an
identifier indicating the RRP message. A HoA field (Home address)
232 indicates the home address of the interface of the HAT. In this
embodiment, the interface of the HAT is any one of the 1xEv-DO IF
34, the WLAN IF 39, the WiMAX IF 44, and the wire-line IF 49. An HA
233 indicates the address of a home agent. A CoA field 234
indicates the care-of address of the interface of the HAT. An ID
field 235 indicates information for checking whether the message is
correct.
[Example of Format of ADR Message]
FIG. 22 shows an example of the format of the ADR message
transmitted from the HAT to the AGW. A Control field 240 indicates
control information, and includes an identifier indicating the ADR
message and a flag designating whether to add the next address
information to the ADR table stored in the storage unit 82 of the
AGW or discard the address information. A NumAddr field 241
indicates the number of sets of the next address information. In
this embodiment, n sets of address information are continued.
Address information is designated in AddrInfo_1, AddrInfo_2, and
AddrInfo_n in the format of a structure 239. An HAT ID field 245
indicates a unique identifier of the HAT. A Sys ID field 246
indicates an identifier for specifying the kind of interface of the
HAT. For example, the Sys ID field 246 specifies the wire-line
access network, the 1xEv-DO system, the wireless LAN, or the WiMAX
system. A HoA (home address) field 247 indicates the home address
of the interface of the HAT. An HA field 248 indicates the address
of the home agent. A CoA field 249 indicates the care-of address of
the interface of the HAT.
For example, an example in which the HAT 19 sets the IP address
information of the WLAN IF 39 in the table of the AGW using the
packet 123 will be described below. The control unit 31 of the HAT
19 sets the flag of the Control 240 such that the next address
information is added to the ADR table. Since the address
information of one wireless LAN interface is transmitted, the
control unit 31 sets `1` to the NumAddr field 241. The next address
information is only AddrInfo_1. It is assumed that, as the IP
address of the WLAN IF 39, the home address is HoA_1, the home
agent address is HA_1, and the care-of address is CoA_1. The
control unit 31 sets an identifier of the HAT 19 to the HAT ID
field 245, and sets an identifier indicating the wireless LAN to
the Sys ID field 246. The control unit 31 sets HoA_1, HA_1, and
CoA_1 to the HoA field 247, the HA field 248, and the CoA field
249, respectively.
The control unit 31 of the HAT 19 may set the flag of the Control
240 such that the next address information is deleted from the ADR
table. In this case, the control unit 83 of the AGW 4 receiving the
packet 123 deletes the next address information from the ADR table
of the storage unit 82 according to the flag of the Control
240.
[Example of Format of HOR Message]
FIG. 23 shows an example of the format of the HOR message for the
AGW to request the HAT to perform a handover. A Control field 251
indicates control information, and includes an identifier
indicating the HOR message and an identifier indicating the format
of the next message. A SsysInfo field 252 indicates information of
an access system, which is a handover source. An HAT ID field 253
indicates an identifier of the HAT requesting handover. A Sys ID
field 254 indicates an identifier of the access system, which is a
handover source.
For example, an example in which the AGW 4 of the 1xEv-DO system
requests the HAT 19 to perform a handover to access systems other
than the 1xEv-DO system using a packet 104 will be described below.
The control unit 83 of the AGW 4 sets the identifier of the HAT 19
to the HAT ID field 253, and sets an identifier indicating the
1xEv-DO system to the Sys ID field 254. The control unit 31 of the
HAT 19 having received the packet 104 analyzes the message, selects
one available access system other than the access system designated
by the Sys ID field 254, and performs a handover to the selected
access system. In this embodiment, the 1xEv-DO system is set to the
Sys ID field 254. For example, assuming that only the wireless LAN
is available other than the 1xEv-DO system, the HAT 19 selects the
wireless LAN and starts the handover.
FIG. 24 shows another example of the format of the HOR message. A
Control field 255 indicates control information, and includes an
identifier indicating the HOR message and an identifier indicating
the format of the next message. A SsysInfo field 252 indicates
information of an access system, which is a handover source,
similar to FIG. 23. An HAT ID field 253 indicates an identifier of
the HAT requesting handover. A Sys ID field 254 indicates an
identifier of the access system, which is a handover source. A
TsysInfo field 256 indicates information of an access system, which
is a handover source. An HAT ID field 257 indicates an identifier
of the HAT requesting handover. A Sys ID field 258 indicates an
identifier of the access system, which is a handover source.
An example in which the AGW 4 of the 1xEv-DO system requests the
HAT 19 to perform a handover to the WLAN RAN 9 using a packet 127
will be described below. The control unit 83 of the AGW 4 sets the
identifier of the HAT 19 to the HAT ID field 253, and sets an
identifier indicating the 1xEv-DO system to the Sys ID field 254.
In addition, the control unit 83 of the AGW 4 sets the identifier
of the HAT 19 to the HAT ID field 257, and sets an identifier
indicating the wireless LAN to the Sys ID field 258.
This message is converted into a packet 128 by the HA 17 and then
transmitted to the HAT 19. The control unit 31 of the HAT 19 having
received the packet 128 analyzes the message, and starts a handover
to the access system designated by the TsysInfo field 256. Since an
identifier indicating the wireless LAN is set to the Sys ID field
258 of the TsysInfo field 256, the control unit 31 of the HAT 19
starts a handover to the WLAN RAN 9. In this embodiment, the
message includes information (SsysInfo field 252) of the access
system, which is a handover source, and information (TsysInfo field
256) of the access system, which is a handover destination.
However, the message may not include the information of the access
system, which is a handover source.
FIG. 25 shows still another example of the format of the HOR
message. A Control field 259 indicates control information, and
includes an identifier indicating the HOR message and an identifier
indicating the format of the next message. A SsysInfo field 252
indicates information of an access system, which is a handover
source, similar to FIG. 23. A TsysList field 260 indicates
information of plural access systems, which are handover
destinations, and the format thereof is shown in FIG. 26. A TsysNum
field 261 indicates the number of access systems, which are the
handover destinations. A TSysInfo_1 field, a TSysInfo_2 field, and
a TSysInfo_k field indicate information of the access systems,
which are the handover destinations, and the format thereof is the
same as that of the TsysInfo field 256. That is, each of the
TSysInfo_1 field, the TSysInfo_2 field, and the TSysInfo_k includes
the HAT ID field 257 and the Sys ID field 258. The HAT ID field 257
indicates an identifier of the HAT requesting handover, and the Sys
ID field 258 indicates an identifier of the access system, which is
a handover destination.
An example in which the AGW 4 of the 1xEv-DO system requests the
HAT 19 to perform a handover to any one of three access systems,
that is, the WLAN RAN 9, the WiMAX RAN 13, and the wire-line access
network 3 will be described below. The control unit 83 of the AGW 4
can select the access systems, which are handover destinations,
from the ADR table of the storage unit 82. The control unit 83 of
the AGW 4 sets an identifier of the HAT 19 to the HAT ID field 253,
and sets an identifier indicating the 1xEv-DO system to the Sys ID
field 254. In addition, the control unit 83 of the AGW 4 sets `3`
to the TsysNum field 261. The control unit 83 of the AGW 4 sets the
identifier of the HAT 19 to the HAT ID field 257 of the TSysInfo_1
field and sets an identifier indicating the wireless LAN to the Sys
ID field 258. The control unit 83 of the AGW 4 sets the identifier
of the HAT 19 to the HAT ID field 257 of the TSysInfo_2 field and
sets an identifier indicating the WiMAX system to the Sys ID field
258. The control unit 83 of the AGW 4 sets the identifier of the
HAT 19 to the HAT ID field 257 of the TSysInfo_3 field and sets an
identifier indicating the wire-line access network to the Sys ID
field 258.
The HAT 19 receiving the message selects one access system from the
wireless LAN, the WiMAX system, and the wire-line access network,
and starts a handover. The HAT 19 may select the access system in
the order of TSysInfo_1, TSysInfo_2, and TSysInfo_3. In this case,
the control unit 31 of the HAT 19 selects the identifier indicating
the wireless LAN that is set to the Sys ID field 258 of the
TSysInfo_1 field, and starts a handover to the WLAN RAN 9.
Only the identifier of the HAT (HAT ID) and the identifier of the
access system (Sys ID) are stored in the SsysInfo field 252 and the
TsysInfo field 256 etc of the HOR messages shown FIGS. 23, 24, 25,
and 26. However, IP address information (HoA, HA, and CoA) may be
additionally stored in these fields. When creating the HOR message,
the control unit 83 of the AGW can obtain this information with
reference to the ADR table stored in the storage unit 82.
[Example of AGW QoS Table]
FIGS. 27 and 28 show an example of QoS information stored in the
storage unit 82 of the AGW 4. The AGW 4 manages QoS information (R
QoS: Requested QoS) requested by the HAT 19 and QoS information (G
QoS: Granted QoS) granted by the network. An example of exchange
between the QoS information items is disclosed in X.P0011-D,
Chapter 4. For example, it is assumed that the exchange between the
QoS information items is performed by the message exchange
represented by reference numeral 114 in FIG. 13.
FIG. 27 shows an example of the format of R QoS. A User ID field
270 indicates a user identifier of the HAT 19. A Num Flow field 271
indicates the number of IP flows stored in the R QoS. In this
embodiment, the number of flows is j. QoS requested by the HAT 19
for each flow is designated to an R QoS (Flow ID 1) field 272, an R
QoS (Flow ID 2) field 273, . . . , an R QoS (Flow ID j) field
274.
For example, the R QoS (Flow ID 1) field is a structure 296 in
which QoS requested by the HAT 19 is designated for an IP flow
having a flow ID of 1. This is similarly applied to the case in
which a flow ID is equal to or greater than 2. A Flow ID field 275
indicates an identifier of the IP flow to which QoS designated to
the structure 296 is applied. An information length (Length) field
276 indicates the sum of the lengths of information items 276, 277,
278, 279, . . . , 280. A Num Set field 277 indicates the number of
sets of QoS parameters stored in the structure 296. In this
embodiment, it is assumed that the number of sets is m. Sets of QoS
parameters requested by the HAT 19 are designated to an R QoS (Set
ID 1) field 278, an R QoS (Set ID 2) field 279, . . . , an R QoS
(Set ID m) field 280. The HAT 19 designates the R QoS (Set ID I)
field 278, the R QoS (Set ID 2) field 279, . . . , the R QoS (Set
ID m) field 280 in the desired order.
For example, the R QoS (Set ID 1) field indicates a structure 297
in which a QoS parameter having a set ID of 1 is designated. The
format of the structure is the same as that in which a set ID is
equal to or greater than 2. A Set Length field 281 indicates the
sum of the lengths of information items in the structure 297. A Set
ID field indicates an identifier of the set of QoS parameters
stored in the structure 297. A Traffic class field 283 designates a
traffic class, such as conversation, streaming, or background. A
Priority field 284 designates priority for granting QoS and
allocating a wireless resource. A Peak rate field 285 designates a
transmission rate at the time of peak. A Max latency field 286
designates an allowable maximum latency. A Max loss rate field 287
designates an allowable maximum data loss rate. A Max jitter field
288 designates an allowable maximum jitter.
FIG. 28 shows an example of the format of G QoS. A User ID field
289 indicates a user identifier of the HAT 19. A Num Flow field 290
indicates the number of IP flows stored in the G QoS. In this
embodiment, the number of flows is j. QoS allocated to the IP flows
having flow IDs of 1, 2, . . . , j is designated to a G QoS (Flow
ID 1) field 291, a G QoS (Flow ID 2) field 292, . . . , a G QoS
(Flow ID j) field 293.
For example, the G QoS (Flow ID 1) field indicates a structure 298
in which QoS allocated to the IP flow having a flow ID of 1 is
designated. The format of the structure is the same as that in
which a flow ID is equal to or greater than 2. A Flow ID field 294
indicates an identifier of the IP flow to which QoS designated to
the structure 298 is applied. A Set ID field 295 indicates an
identifier indicating a set of QoS parameters.
[Example of AGW ADR Table]
FIGS. 29, 30, 31, and 32 show examples of the ADR table stored in
the storage unit 82 of the AGW. The control unit 83 of the AGW
receives the ADR message shown in FIG. 22 from the HAT, and
registers information in the ADR table. In these examples, it is
premised that the HATs 19 and 20 are connected to the access
networks, as shown in FIG. 34.
That is, the HAT 19 is connected to the 1xEv-DO RAN 5, the WLAN RAN
9, and the wire-line access network 3. The home address (HoA) of
the 1xEv-DO IF 34 of the HAT 19 is HoA_5, the home agent address
(HA) is HA_5, and the care-of address (CoA) is CoA_5. The home
address (HoA) of the WLAN IF 39 of the HAT 19 is HoA_1, the home
agent address (HA) is HA_1, and the care-of address (CoA) is CoA_1.
The home address (HoA) of the wire-line IF 49 of the HAT 19 is
HoA_2, the home agent address (HA) is HA_2, and the care-of address
(CoA) is CoA_2.
The HAT 20 is connected to the 1xEv-DO RAN 5, the WLAN RAN 9, and
the WiMAX RAN 13. The home address (HoA) of the 1xEv-DO IF 34 of
the HAT 20 is HoA_6, the home agent address (HA) is HA_6, and the
care-of address (CoA) is CoA_6. The home address (HoA) of the WLAN
IF 39 of the HAT 20 is HoA_3, the home agent address (HA) is HA_3,
and the care-of address (CoA) is CoA_3. The home address (HoA) of
the WiMAX IF 44 of the HAT 20 is HoA_4, the home agent address (HA)
is HA_4, and the care-of address (CoA) is CoA_4.
FIG. 29 shows an example of the ADR table recorded in the storage
unit 82 of the AGW 4. An HAT ID field 301 indicates an identifier
of the HAT. A Sys ID field 302 indicates an identifier of the
access system. An HoA field 303 indicates a home address. An HA
field 304 indicates an address of a home agent. A CoA field 305
indicates a care-of address. Information in a row 310 is the
address information of the WLAN IF 39 of the HAT 19. Information in
a row 311 is the address information of the wire-line IF 49 of the
HAT 19. Information in a row 312 is the address information of the
WLAN IF 39 of the HAT 20. Information in a row 313 is the address
information of the WiMAX IF 13 of the HAT 20.
FIG. 30 shows an example of the ADR table recorded in the storage
unit 82 of the AGW 8. An HAT ID field 301 indicates an identifier
of the HAT. A Sys ID field 302 indicates an identifier of the
access system. An HoA field 303 indicates a home address. An HA
field 304 indicates an address of a home agent. A CoA field 305
indicates a care-of address. Information in a row 314 is the
address information of the 1xEv-DO IF 34 of the HAT 19. Information
in a row 315 is the address information of the wire-line IF 49 of
the HAT 19. Information in a row 316 is the address information of
the 1xEv-DO IF 34 of the HAT 20. Information in a row 317 is the
address information of the WiMAX IF 13 of the HAT 20.
FIG. 31 shows an example of the ADR table recorded in the storage
unit 82 of an AGW 2. An HAT ID field 301 indicates an identifier of
the HAT. A Sys ID field 302 indicates an identifier of the access
system. An HoA field 303 indicates a home address. An HA field 304
indicates an address of a home agent. A CoA field 305 indicates a
care-of address. Information in a row 318 is the address
information of the WLAN IF 39 of the HAT 19. Information in a row
319 is the address information of the 1xEv-DO IF 34 of the HAT 19.
Since the HAT 20 is not connected to the AGW 2, address information
related to the HAT 20 is not registered in the table.
FIG. 32 shows an example of the ADR table recorded in the storage
unit 82 of an AGW 12. An HAT ID field 301 indicates an identifier
of the HAT. A Sys ID field 302 indicates an identifier of the
access system. An HoA field 303 indicates a home address. An HA
field 304 indicates an address of a home agent. A CoA field 305
indicates a care-of address. Information in a row 320 is the
address information of the 1xEv-DO IF 34 of the HAT 20. Information
in a row 321 is the address information of the WLAN IF 39 of the
HAT 20. Since the HAT 19 is not connected to the AGW 12, address
information related to the HAT 19 is not registered in the
table.
FIGS. 29, 30, 31, and 32 show examples in which one IP address
corresponds to each of the interfaces of the access systems of the
HATs 19 and 20. However, plural IP addresses may be allocated to
the interface of one access system. In this case, in the storage
unit 83 of the AGW 8, IP address information is also included in
the HOR message. Therefore, it is possible to request the HAT to
perform a handover in the unit of IP flow.
The control unit 83 of the AGW adds information to ADR table or
deletes information from the ADR table according to the flag in the
Control field 240 of the ADR message. When a predetermined time has
elapsed after the communication of a certain IP flow is
interrupted, the control unit 83 of the AGW may delete the address
information of the IP flow from the ADR table. The AGW can count
the time for which each IP flow does not communicate using the
timer 85.
[Example of HA Table]
FIG. 33 shows an example of the address information table of the
HAT recorded in the storage unit 88 of the HA 17. The control unit
89 of the HA 17 registers information of the RRQ message received
by the NW IF of the HAT in the table.
In the example, it is premised that the HATs 19 and 20 are
connected to the access networks, as shown in FIG. 34. A Control
field 331 indicates control information. An HoA field 332 indicates
the home address of the HAT for the interface of the access
system.
In this embodiment, the interface is any one of the 1xEv-DO IF 34,
the WLAN IF 39, the WiMAX IF 44, and the wire-line IF 49. An HA
field 333 indicates the address of the home agent of the interface.
A CoA field 334 indicates the care-of address of the interface. An
ID field 335 indicates information for checking whether the message
is correct. Information in a row 341 is the address information of
the WLAN IF 39 of the HAT 19. Information in a row 342 is the
address information of the wire-line IF 49 of the HAT 19.
Information in a row 343 is the address information of the WLAN IF
39 of the HAT 20. Information in a row 344 is the address
information of the WiMAX IF 13 of the HAT 20. Information in a row
345 is the address information of the 1xEv-DO IF 34 of the HAT 19.
Information in a row 346 is the address information of the 1xEv-DO
IF 34 of the HAT 20.
[Example of Algorithm for Determining HOR Transmitting Chance]
FIG. 35 shows an example of an algorithm for determining an HOR
message transmitting chance performed by the control unit 83 of the
AGW. In Step 1, it is determined whether an IP flow 144 is in an
Xoff state. The Xoff state means that the AGW receives a packet
transmission stop signal 23 for the IP flow, but does not receives
a packet transmission resume signal 24.
If the IP flow is in the Xoff state, in Step 2, the control unit 83
of the AGW determines whether the capacity of the buffer
transmitting the IP flow 144 provided in the storage unit 82 is
larger than a threshold value. If it is determined that the
capacity of the buffer transmitting the IP flow 144 provided in the
storage unit 82 is larger than the threshold value, in Step 3, the
control unit 83 of the AGW transmits an HOR message. For example,
the control unit 83 creates a packet 147 including the HOR message,
and transmits the packet to the HAT 19 through the NW IF 87.
In this flow, Step 2 may not be performed, and Step 1 may directly
proceed to Step 3 if the IP flow is in the Xoff state. When a large
load is applied to the access network, the AGW may transmit the HOR
message at the beginning, without depending on the state of the
transmission buffer.
FIG. 36 shows another example of the algorithm for determining the
HOR message transmitting chance performed by the control unit 83 of
the AGW. In Step 1, it is determined whether the IP flow 144 is in
an Xoff state. The Xoff state means that the AGW receives a packet
transmission stop signal 23 for the IP flow, but does not receives
the packet transmission resume signal 24. If the IP flow is in the
Xoff state, in Step 2, the control unit 83 of the AGW determines
whether the capacity of the buffer transmitting the IP flow 144
provided in the storage unit 82 is larger than a threshold value.
If it is determined that the capacity of the buffer transmitting
the IP flow 144 provided in the storage unit 82 is larger than the
threshold value, in Step 4, the control unit 83 determines whether
to perform the handover of the IP flow 144.
For example, in Step 4, when the control unit 83 generates uniform
random numbers [0, 1] and the random numbers are larger than 0.5,
the control unit determines to perform the handover of the IP flow
144.
In Step 4, if it is determined to perform the handover of the IP
flow 144, in Step 3, the control unit 83 of the AGW transmits the
HOR message. For example, the control unit 83 creates a packet 147
including the HOR message, and transmits the packet to the HAT 19
through the NW IF 87. As shown in FIG. 35, when a handover is
collectively performed on all the IP flows satisfying the
conditions, the handover is performed on the same destination,
which results in load concentration. In Step 4 of FIG. 36, it is
possible to distribute the load by selecting the IP flow subjected
to handover.
As such, according to this embodiment, the AGW randomly determines
the message transmitting chance during the determination of a
predetermined message transmitting chance. When the AGW
collectively performs a handover on all the IP flows having
received the packet transmission stop signals, a load may be
concentrated on the handover destination. However, since the
handover is randomly performed, it is possible to distribute the
load.
FIG. 37 shows still another example of the algorithm for
determining the HOR message transmitting chance performed by the
control unit 83 of the AGW. In Step 1, it is determined whether the
IP flow 144 is in an Xoff state. The Xoff state means that the AGW
receives a packet transmission stop signal 23 for the IP flow, but
does not receives the packet transmission resume signal 24. If the
IP flow is in the Xoff state, in Step 5, the control unit 83 of the
AGW examines the deterioration of QoS of the IP flow 144. If
deterioration of QoS of the IP flow 144 is detected, in Step 3, the
control unit 83 of the AGW transmits the HOR message. For example,
the control unit 83 creates the packet 147 including the HOR
message, and transmits the packet to the HAT 19 through the NW IF
87.
As an example of Step 5, the control unit 83 of the AGW measures
the loss rate of the IP packet of the IP flow 144 stored in the
storage unit 82. In addition, the control unit 83 compares the
measure loss rate of the IP packet with the loss rate (Max loss
rate 287) of the IP packet granted by the IP flow 144, and
determines whether the measure loss rate of the IP packet is higher
than the Max loss rate 287. When it is determined that the measured
loss rate is higher than the Max loss rate 287, the control unit
determines that QoS of the IP flow 144 deteriorates.
As another example of Step 5, the control unit 83 of the AGW
measures the retention time for which the IP packet of the IP flow
144 is stored in the storage unit 82. In addition, the control unit
83 compares the measured retention time of the IP packet with an
allowable maximum latency (Max latency 286) of the IP packet
granted by the IP flow 144, and determines whether the measured
retention time of the IP packet is longer than the Max latency 286.
When the measured retention time is longer than the Max latency
286, the control unit determines that QoS of the IP flow 144
deteriorates.
As such, according to this embodiment, when the measure
communication quality is lower than QoS stored in the storage unit,
the AGW determines that the message transmitting chance is given.
When each access system cannot absorb a traffic load and the
communication quality deteriorates, the access system that is
currently being used is switched to another access system.
Therefore, it is possible to prevent the deterioration of the
communication quality.
FIG. 38 shows yet another example of the algorithm for determining
the HOR message transmitting chance performed by the control unit
83 of the AGW. In Step 1, it is determined whether the IP flow 144
is in an Xoff state. The Xoff state means that the AGW receives the
packet transmission stop signal 23 for the IP flow, but does not
receives the packet transmission resume signal 24. If the IP flow
is in the Xoff state, in Step 6, the control unit 83 of the AGW
determines whether to perform a handover on a QoS parameter of the
IP flow 144. When it is determined that a handover should be
performed on the QoS parameter of the IP flow 144, in Step 2, the
control unit 83 of the AGW determines whether the capacity of the
buffer transmitting the IP flow 144 provided in the storage unit 82
is larger than a threshold value. If it is determined that the
capacity of the buffer transmitting the IP flow 144 provided in the
storage unit 82 is larger than the threshold value, in Step 3, the
control unit 83 of the AGW transmits the HOR message. For example,
the control unit 83 creates the packet 147 including the HOR
message, and transmits the packet to the HAT 19 through the NW IF
87.
For example, in Step 6, the control unit 83 determines whether to
perform a handover on the QoS parameter, on the basis of the QoS
information of the IP flow 144 stored in the storage unit 82. The
control unit 83 can specify the QoS parameter allocated to the IP
flow 144, on the basis of a Set ID field 295 for the IP flow 144 of
G_QoS. The control unit 83 searches a QoS parameter set 297
corresponding to a Set ID field 295 from a Set ID field 282 of
R_QoS. Further, for example, when the value of a priority 284 is
larger than a predetermined value, the control unit 83 performs a
handover on the IP Flow 144 on the basis of the priority 284 of the
searched QoS parameter set 297.
As another example of Step 6, the control unit 83 searches a QoS
parameter set 297 corresponding to a Set ID field 295 from a Set ID
field 282 of R_QoS. For example, the control unit 83 performs a
handover on the IP flow 144 only when the value of a Traffic class
field 283 is not `background`, on the basis of the value of the
Traffic class field 283 of the searched QoS parameter set 297.
As still another example of Step 6, the control unit 83 searches a
QoS parameter set 297 corresponding to the Set ID field 295 from
the Set ID field 282 of R_QoS. For example, the control unit 83
performs a handover on the IP flow 144 when the value of the Max
loss rate field 287 is smaller than a predetermined value, on the
basis of the value of the Max loss rate field 287 of the searched
QoS parameter set 297.
As yet another example of Step 6, the control unit 83 searches a
QoS parameter set 297 corresponding to the Set ID field 295 from
the Set ID field 282 of R_QoS. For example, the control unit 83
performs a handover on the IP flow 144 when the value of the Max
latency field 287 is smaller than a predetermined value, on the
basis of the value of the Max latency field 287 of the searched QoS
parameter set 297.
As such, according to this embodiment, the AGW can perform a
handover between different types of access systems only when it is
necessary to maintain the communication quality provided to a
terminal.
FIG. 39 shows still yet another example of the algorithm for
determining the HOR message transmitting chance performed by the
control unit 83 of the AGW. In Step 1, it is determined whether the
IP flow 144 is in an Xoff state. The Xoff state means that the AGW
receives the packet transmission stop signal 23 for the IP flow,
but does not receives the packet transmission resume signal 24. If
the IP flow is in the Xoff state, in Step 6, the control unit
determines whether to perform a handover on a QoS parameter of the
IP flow 144. When it is determined that a handover should be
performed on the QoS parameter of the IP flow 144, in Step 5, the
control unit 83 of the AGW examines the deterioration of QoS of the
IP flow 144. If the deterioration of QoS of the IP flow 144 is
detected, in Step 3, the control unit 83 of the AGW transmits the
HOR message. For example, the control unit 83 creates the packet
147 including the HOR message, and transmits the packet to the HAT
19 through the NW IF 87.
As such, according to this embodiment, the AGW determines that the
message transmitting chance is given when the measured
communication quality is lower than that stored in the storage
unit. When each access system cannot absorb a traffic load and the
communication quality deteriorates, the access system that is
currently being used is switched to another access system.
Therefore, it is possible to prevent the deterioration of the
communication quality.
Further, according to this embodiment, the AGW can perform a
handover between different types of access systems only when it is
necessary to maintain the communication quality provided to a
terminal.
In FIG. 1, the AGW is separated from the PCF or the H/R, but the
AGW may be integrally formed with the PCF or the H/R. In this case,
it is determined whether the HOR message transmitting chance is
given on the basis of whether the packet stop signal transmitted
from the AP, not the packet stop signal transmitted from the
integrated structure of the AGW and the PCF or the H/R, is
received.
Furthermore, in FIG. 1, for example, the wire-line access network,
the 1xEv-DO system, the wireless LAN, and the WiMAX system are used
as communication methods between the HAT and the access network,
but radio communication methods to which the invention is applied
are not limited thereto. For example, the invention can be applied
to other radio communication methods, such as PHS, GSM, and
W-CDMA.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram illustrating an example of the structure of a
wireless system according to the present invention;
FIG. 2 is a diagram illustrating an example of the structure of a
terminal according to a first embodiment of the present
invention;
FIG. 3 is a diagram illustrating an example of the structure of a
base station according to the first embodiment of the present
invention;
FIG. 4 is a diagram illustrating an example of the structure of a
network system according to the first embodiment of the present
invention;
FIG. 5 is a diagram illustrating an example of the structure of a
packet control device according to the first embodiment of the
present invention;
FIG. 6 is a diagram illustrating an example of the structure of a
traffic control unit according to the first embodiment of the
present invention;
FIG. 7 is a diagram illustrating an example of the structure of an
access gateway according to the first embodiment of the present
invention;
FIG. 8 is a diagram illustrating an example of the structure of a
home agent according to the first embodiment of the present
invention;
FIG. 9 is a diagram illustrating an example of the structure of a
node apparatus according to the first embodiment of the present
invention;
FIG. 10 is a diagram illustrating an example of a priority control
method according to the first embodiment of the present
invention;
FIG. 11 is a diagram illustrating an example of a call flow of a
handover between systems according to the first embodiment of the
present invention;
FIG. 12 is a diagram illustrating an example of a call flow of a
handover between systems according to another embodiment of the
present invention;
FIG. 13 is a diagram illustrating an example of a call flow of a
handover between systems according to still another embodiment of
the present invention;
FIG. 14 is a diagram illustrating an example of a call flow of a
handover between systems according to yet embodiment of the present
invention;
FIG. 15 is a diagram illustrating an example of a packet format
according to the present invention;
FIG. 16 is a diagram illustrating another example of the packet
format according to the present invention;
FIG. 17 is a diagram illustrating still another example of the
packet format according to the present invention;
FIG. 18 is a diagram illustrating yet another example of the packet
format according to the present invention;
FIG. 19 is a diagram illustrating still yet another example of the
packet format according to the present invention;
FIG. 20 is a diagram illustrating an example of an RRQ message
format;
FIG. 21 is a diagram illustrating an example of an RRP message
format;
FIG. 22 is a diagram illustrating an example of a message format
according to the present invention;
FIG. 23 is a diagram illustrating another example of the message
format according to the present invention;
FIG. 24 is a diagram illustrating still another example of the
message format according to the present invention;
FIG. 25 is a diagram illustrating yet another example of the
message format according to the present invention;
FIG. 26 is a diagram illustrating still yet another example of the
message format according to the present invention;
FIG. 27 is a diagram illustrating an example of a table of an
access gateway according to the invention;
FIG. 28 is a diagram illustrating another present example of the
table of the access gateway according to the invention;
FIG. 29 is a diagram illustrating still another example of the
table of the access gateway according to the present invention;
FIG. 30 is a diagram illustrating yet another example of the table
of the access gateway according to the present invention;
FIG. 31 is a diagram illustrating still yet another example of the
table of the access gateway according to the present invention;
FIG. 32 is a diagram illustrating yet still another example of the
table of the access gateway according to the present invention;
FIG. 33 is a diagram illustrating an example of a table of a home
agent according to the present invention;
FIG. 34 is a diagram illustrating an example of the structure of a
wireless system according to the first embodiment of the present
invention;
FIG. 35 is a flowchart illustrating an algorithm for determining a
signal transmitting chance according to the first embodiment of the
present invention;
FIG. 36 is a flowchart illustrating an algorithm for determining a
signal transmitting chance according to another embodiment of the
present invention;
FIG. 37 is a flowchart illustrating an algorithm for determining a
signal transmitting chance according to still another embodiment of
the invention;
FIG. 38 is a flowchart illustrating an algorithm for determining a
signal transmitting chance according to yet another embodiment of
the present invention;
FIG. 39 is a flowchart illustrating an algorithm for determining a
signal transmitting chance according to still yet another
embodiment of the present invention; and
FIG. 40 is a diagram illustrating an example of a flow control
method.
EXPLANATION OF LETTERS OR NUMERALS
1 . . . ,2,4,8,12 . . . AGW, 6 . . . PCF, 10,14,18 . . . H/R,
7,11,15 . . . AP, 19,20 . . . HAT, 16 . . . CN, 17 . . . HA, 23 . .
. a packet transmission stop signal, 24 . . . a packet transmission
start signal, 34 . . . a 1xEv-DO interface (1xEv-DO IF), 39 . . .
WLAN IF, 44 . . . WiMAX IF, 49 . . . Wire-line IF, 103,109,126,146
. . . message transmitting chance.
* * * * *